Field of the Disclosure
The present disclosure, for example, relates to wireless communication systems, and more particularly to a listen-before-talk mechanism that supports direct communications on an unlicensed radio frequency spectrum band.
Description of Related Art
Wireless communication systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include code-division multiple access (CDMA) systems, time-division multiple access (TDMA) systems, frequency-division multiple access (FDMA) systems, and orthogonal frequency-division multiple access (OFDMA) systems.
By way of example, a wireless multiple-access communication system may include a number of base stations, each simultaneously supporting communication for multiple communication devices, otherwise known as user equipments (UEs). A base station may communicate with UEs on downlink channels (e.g., for transmissions from a base station to a UE) and uplink channels (e.g., for transmissions from a UE to a base station). UEs may communicate directly with each other using direct-to-direct (D2D) communications over a direct D2D wireless link.
Current implementations provide for D2D communications in band(s) of a licensed radio frequency spectrum and/or an unlicensed radio frequency spectrum band. Communications in the unlicensed radio frequency spectrum band, however, may comply with various requirements regarding medium access procedures, for example. The UEs may synchronize their D2D communications using wireless wide area network (WWAN) resources, e.g., LTE bands.